A block guard operation may associate a data integrity field with a fixed size user data field. For example, a eight byte data integrity field may be associated with a 512 byte user data field. The data integrity field may add an extra layer of protection to the user data field against errors, such as, multi-bit Error Correcting Code (ECC) errors, etc. Data integrity field may be appended to the data blocks of a data stream. Data blocks that include both the user data field and the data integrity field may be referred to as expanded data blocks, while data blocks that include only the user data field may be referred to as compressed data blocks. Further details of the block guard operation and data integrity fields are described in the publications entitled “SPC-3; SBC-2; Simplified End-to-End Data Protection” (Document number 03-365R1) authored by George O. Penokie, published on Nov. 06, 2003 by the T10 Technical Committee, and “SBC, 32 Byte Commands for End-to-End Data Protection” (Document number 03-307R7), authored by Jim Coomes, published on Mar. 19, 2004 by the T10 Technical Committee.
Redundant Array of Independent Disks (RAID) is a mechanism for making disks fault tolerant. RAID may use an ECC, known as parity, to recover from single point of failure errors, i.e., the failure of a single disk. RAID may stripe the data and parity across a plurality of disks to improve the speed of data retrieval and at the same time allow for fault tolerance. There are a number of different RAID levels, such as, RAID level 0, 1, 2, 3, 4, 5. RAID level 5 provides data striping at the byte level and also provides stripe error correction information. In RAID level 5, the parity corresponding to data on a plurality of disks may be computed and the parity may be used to recover from a disk failure without losing any data.